This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. (1) Mitochondria play a central in role energy metabolism, calcium signaling, aging, and cell death. Despite their importance, only few structures of mitochondrial membrane protein have been solved so far. We crystallized one of the human mitochondrial proteins and wish to perform diffraction experiments to solve its structure. The resulting structure will shed a light on how these mitochondrial membrane proteins exert their functions. (2) Voltage-gated calcium channels (Cavs) are multi-subunit macromolecules that control calcium entry into cells upon membrane depolarization. Calmodulin (CaM) plays a critical role in calcium-dependent modulation of CaVs through association with the Cav ?1 C-terminus. Although a multitude of functional studies of the CaV-CaM interaction have been carried out, the structural details of CaM modulation of CaVs remain unclear. To elucidate the structural basis of CaV regulation, we have prepared crystals of different CaM states in complexes with different lengths of CaM binding motifs from CaV ?1 C-terminus.